Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners may be used in forming print and/or xerographic images. Emulsion aggregation techniques may involve the formation of a polymer emulsion by heating a monomer and undertaking a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210, 5,994,020, and U.S. Patent Application Publication No. 2008/0107989, the disclosures of each of which are hereby incorporated by reference in their entirety.
Polyester toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety. The incorporation of these polyesters into the toner requires that they first be formulated into emulsions prepared by solvent containing batch processes, for example solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE), which is both time and energy-consuming. In both cases, large amounts of organic solvents, such as ketones or alcohols, have been used to dissolve the resins, which may require subsequent energy intensive distillation to form the latexes, and are not environmentally friendly.
Solventless latex emulsions have been formed in either a batch or extrusion process through the addition of a neutralizing solution, a surfactant solution and water to a thermally softened resin as illustrated, for example, in U.S. patent application Ser. Nos. 12/032,173 and 12/056,529, the disclosures of each of which are hereby incorporated by reference in their entirety. However, a small amount of coarse material remains un-emulsified in these processes and so the conversion of the resin to the latex is not complete. The latexes must therefore be treated to remove this coarse content or a polishing step must be added to convert the residual resin or coarse material into latex particles. For example filtration may be used to remove any coarse material while ultrasonication, and/or homogenization using external high shear devices may be applied to the latex produced from the extruder to complete the conversion. The additional process steps are however not desirable as they add complexity, energy consumption and cost.
It would be advantageous to provide a process for the preparation of a polymer latex suitable for use in a toner product that is more efficient, takes less time, and has a high product yield.